Abstract: A mehtod for mixing water and diesel fuel in a ratio between 5 and 20 Vol %, in which the liquid components are recirculated in a recirculation loop comprising an ellipsoidal vortex chamber (10) in which rotation around a longitudinal axis (9) is attained, the rotating fluid is expanded and tangentially injected in a baloon-like second vortex chamber (16) with an axis (17) normal to that of the first chamber, the open lower end of the second rotational chamber (16) is connected to fluid inlets and suction side of a recirculating pump. The outlet occurs from the equatorial plane of the second vortex chamber. The outflow rate should be at least ten times less than the flow in the recirculation loop. The mixture which have water droplets smaller than 200 nm has a consistency similar to that of fuel and can be used as fuel to diesel engines, whereby the amount of unwanted components in the exhaust gases will be reduced.